Black bean, corn and tomato salad

16 ounces packaged dried black beans, rinsed and picked over
5 cups very hot tap water
3 chopped large tomatoes
2 chopped large bell peppers (preferably 1 red, I green)
4 chopped scallions
2 cups corn kernels
1/3 cup red wine vinegar
1/2 cup olive oil
1 1/2 teaspoons ground cumin
1/4 cup chopped cilantro

1. In a 3 1/2-quart electric slow cooker, combine the beans and hot water.
2. Cover and cook on the high heat setting 3 to 4 hours (or on the low heat setting 5 to 7 hours), until the beans are tender but not falling apart.
3. Drain the beans into a colander and rinse with cold water.
4. In a large bowl, combine beans, tomatoes, peppers, corn kernels, vinegar, olive oil, and ground cumin. Season with salt and freshly ground pepper to taste. Stir in cilantro. Serve at room temperature or slightly chilled.